The present invention relates to an infusion apparatus as customarily used in medical technology for supplying solutions or blood substitutes to a patient by infusion. Infusion apparatuses of the kind in question here consist of an indwelling venous cannula, i.e. a catheter holder with a catheter of flexible plastic such as PTFE and a steel cannula holder with a steel cannula disposed on the catheter holder, the steel cannula leading axially through the indwelling venous cannula or the catheter holder and the plastic cannula so that its tip projects at the distal end of the plastic cannula. The steel cannula holder is sealed at the end axially opposite the steel cannula with a Luer lock connection, a kind of screw cap. The Luer lock connection can be removed in order to connect an infusion tube to the steel cannula holder. A thus prepared infusion apparatus is inserted into a vein and advanced as far as possible into the punctured vein. The catheter holder is then fastened to the patient""s skin by means of flexible tabs and the steel cannula holder can subsequently be withdrawn completely from the indwelling venous cannula together with the steel cannula. Only the plastic cannula connected with the catheter holder fixed outside the body remains in the vein. The infusion tube can now be connected directly to the catheter holder rather than to the steel cannula holder.
When the steel cannula is removed there is a free connection between the body vein and the interior of the indwelling cannula or the interior of the channel extending through the housing of the catheter holder. Blood can therefore escape before an infusion tube is connected to the catheter holder. The same applies of course when the infusion tube is changed.
Said escape of blood must be prevented in order both to protect the patient and to protect the caretaking staff, for example nurses and doctors. Direct blood contact must absolutely be avoided in view of a possible infection (HIV, hepatitis).
It is known to avoid such dangers by providing a check valve in the channel extending through the housing of the catheter holder. However, known check valves are constructed of many single parts, accordingly difficult to assemble and also trouble-prone (DE 38 09 127 and DE 41 37 019).
The problem underlying the invention is to provide an infusion apparatus and in particular an indwelling venous cannula which has a simple structure and can thus be produced cost-effectively. Despite the simplicity of its structure the indwelling venous cannula should reliably prevent the danger of unintentional escape of the patient""s blood.
This problem is solved according to the invention by the features of independents claims 1 and 8. Especially preferred embodiments and designs of the inventive indwelling venous cannula are the object of the subclaims.